Is it ensure, insure, or assure?
c.1300, from Old French andier, of unknown origin, perhaps from Gaulish *andero- "a young bull" (cf. Welsh anner "heifer"), which would make sense if they once had bull's heads cast onto them. Altered by influence of Middle English iren (see iron (n.)).
one of a pair of horizontal iron bars upon which wood is supported in an open fireplace. The oldest of fireplace furnishings, andirons were used widely from the Late Iron Age. The andiron stands on short legs and usually has a vertical guard bar at the front to prevent logs from rolling off, thus giving it a somewhat doglike appearance (hence the alternative name, firedog). It was ordinarily fitted with a guard at each end when intended for use in a central open hearth, which went out of general use in the late 14th century. The guard was often cast in the form of a statue or with elaborate decoration. Plain andirons, called cobirons, with ratcheted guards holding brackets for spits, were used in the kitchen.